Tungsten species, which are compounds containing a tungsten atom or atoms as an essential component, show catalytic activity in various reactions and are effective as catalyst components. For example, it is known that supported materials prepared by supporting tungsten species on a support such as alumina, and so on can be used as catalysts for petroleum cracking or alkene isomerization/disproportionation in vapor phase reactions, and it is disclosed that catalysts comprising tungsten oxide supported on a support such as MgO, and so on are useful in 1-butene isomerization and in disproportionation of 1-butene, propylene and ethylene (see e.g. T. Yamaguchi et al, J. Catal., (1987), 65 p. 442-447) There is also a disclosure about the use of alumina-supported tungsten oxide as a catalyst for petroleum cracking (see e.g. L. L. Murrell et al, J. Catal., (1987), 107 p. 463-470).
On the other hand, the method of producing epoxy compounds by carrying out, in the liquid phase, the epoxidation reaction of compounds having at least one ethylenic double bond using an alumina-supported tungsten catalyst and hydrogen peroxide as an oxidizing agent is a useful method and, concerning this method, it is disclosed as follows.
Referring to the method of producing epoxy compound by reacting ethylenic double bond-containing compounds with hydrogen peroxide, it is disclosed that the epoxidation reaction was carried out at 60° C. using allyl alcohol and hydrogen peroxide in a mole ratio of 1.5:1, with a water-hydrogen peroxide mole ratio of 35:1, and using a tungsten species as a supported catalyst (see e.g. U.S. Pat. No. 2,870,171 (specification, columns 2-3, 5, and 8-9)). It is described that, in this epoxidation reaction, the yield was 27 to 31% as expressed in terms of mole percent relative to hydrogen peroxide, with the conversion of hydrogen peroxide of 97.8 to 99.1%. As the supported catalyst, there are mentioned, as tungsten species, H2WO4, NaHWO4, NH4HWO4, Na2WO4, heteropolytungstic acid, heteropolytungstic acid alkali metal or alkaline earth metal salts, and so on, and, as supports, mention is made of alumina, active carbon, magnesia, zirconia, silica-alumina, and clay. Furthermore, H2WO4/Al2O3 (uncalcined) is mentioned in an embodiment.
Furthermore, it is disclosed that compounds represented by Q3XW4O24-2n (wherein Q represents the cation of a quaternary onium salt, X represents a P or As atom, and n represents 0, 1 or 2) are supported on an inert substance, such as alumina, for use as catalysts for epoxidation of olefinic compounds using hydrogen peroxide (see e.g. Laid-open European Patent Application No. 0109273 (specification, pages 13-16, 40)).
Referring to the epoxidation reaction using hydrogen peroxide and tungsten catalysts, it is disclosed that cyclohexene, cyclooctene or 1-octene was used as a substrate and subjected to epoxidation reaction at 60° C. in methanol or tert-butanol as a solvent in a substrate-hydrogen peroxide mole ratio of 1:1 or 1:2 (see e.g. International Laid-open Patent Application No. 93/00338 (pamphlet, pages 16-23, 24). It is described that, in this epoxidation reaction, the conversion amounted to 23-98.1% as expressed in terms of mole percent of substrate and the selectivity for epoxidation to 7-92% as expressed in terms of mole percent of substrate. As for the supported catalysts, mention is made of, as tungsten species, tungsten-containing heteropolyacids, such as M3PWnMo12-nO40 (M representing a counter anion), and, in the embodiments, there are mentioned H3PW12O40—Al2O3, H3PWMo11O40—Al2O3, H3PW12O40—Mg silicate, (CP)3PW12O40—Al2O3, H3PW12O40—ZrPO4, H3PW12O40—SnO2, H3PW12O40—Al(OH)3, H3PW12O40—TiO2, H3PW6Mo6O40—Al2O3, H3PMO12O40—SiO2, and so on. As for the supports, mention is made of solids containing elements selected from the groups IIa, IIb, IIIb, IVa and IVb or organic-based materials such as strong basic resins and, in an embodiment, Al2O3 is mentioned.
In commercial production processes, such catalysts are generally to be reused. Since, however, the catalyst component tungsten species are leached into liquid reaction mixtures and the catalytic activity decreases accordingly, it becomes impossible to reuse the catalysts. Tungsten species are expensive and, therefore, it is desired that the catalysts be rendered reusable. Although it is disclosed that catalyst calcination (see e.g. International Laid-open Patent Application No. 93/00338 (pamphlet, pages 16-23 and 24)) results in reducing catalyst component leaching as compared with the case of no catalyst calcination (see e.g. U.S. Pat. No. 2,870,171 (specification, columns 2-3, 5, and 8-9)), there is still room for contrivance for making it possible to suppress the leaching of catalyst components by some methods other than such a method as mentioned above.
Furthermore, when these catalysts are used, the efficiency of hydrogen peroxide utilization as expressed in terms of the percentage of the portion of hydrogen peroxide consumed for epoxy compound formation relative to the whole amount of hydrogen peroxide used as a reactant is low. Therefore, there is room for contrivance from the viewpoint of improving or maintaining the catalytic activity performance as well.
Meanwhile, there is a report about the analyses of the molecular structures of alumina-supported tungsten oxide catalysts with and without addition of a secondary component metal oxide (see e.g. M. M. Ostromecki et al, J. Mol. Catal., A: Chemical, (1998), 132 p. 43-57). Thus, for WO3/Al2O3, which has been used for long as a petroleum cracking catalyst, analysis was performed of the manner of supporting of metal oxide additives (the metal being Ni, Fe, P, Sn, La, Co, Ce, Zn, etc.) added to this catalyst on the surface thereof. However, there is no disclosure about the use thereof in actual reactions. Thus, there is no disclosure about the possibility of such catalysts being useful in liquid-phase oxidation reactions. Therefore, there is no description of how to prevent catalyst components from leaching and/or improve or maintain the catalytic activity performance in catalytic reactions.
Further, the epoxidation reaction of cyclooctene with hydrogen peroxide has been disclosed in which a catalyst comprising silicon oxide and tungsten oxide supported on MCM-41 (mesoporous molecular sieve) (see e.g. Briot, E. et al, J. Mater. Chem., (2000), 10 p. 953-958). It is described that this epoxidation reaction was carried out using two or more catalysts prepared by different methods of catalyst preparation or by varying the ratio between the silicon species and tungsten species, using the substrate cyclooctene and hydrogen peroxide in a ratio of 1:5, and using tert-butanol as a solvent, to give substrate conversion of 33-98%. As for the supported catalysts, WO(O2)2(H2O)2 and the like are mentioned as the tungsten species, and MCM-41 is mentioned as the support.
The epoxidation reaction of 1-octene with hydrogen peroxide using a catalyst comprising a tungsten species supported on a hydrophobic mesoporous silica gel has been disclosed (see e.g. T. Sakamoto et al, Tetrahedron Letters, (2000), 41 p. 10009-10012). It is described that this epoxidation reaction was carried out at 90° C., using the substrate 1-octene and hydrogen peroxide in a ratio of 1:2, and using two or more catalysts comprising a tungsten species supported on a silica gel support surface-treated with a silane coupling agent and an alkylating agent to give substrate conversion of 18-100%. As for the supported catalysts, [Π-C5H5N+ (CH2)15CH3]3(PW12O40)3− is mentioned as the tungsten species, and SiO2 surface-treated with Ph3SiOC2H5 and (CH3)2NCH(OCH2Ph)2, among others, is mentioned as the support.
The epoxidation reaction of cyclohexene with hydrogen peroxide has been disclosed in which a catalyst comprising a tungsten species supported on a layered support (see e.g. Watanabe, Y. et al, J. Mol. Catal., A: Chemical, (1999), 145 p. 281-289). It is described that this epoxidation reaction was carried out at a temperature of 70° C., using the substrate cyclohexene and hydrogen peroxide in a ratio of 1:1, and using a catalyst comprising K8SiW11O39 or K4SiW12O40 as the tungsten species supported on Zn3Al as the support to give a turnover number of 14 or 1.9 mol/mol-W, respectively.
However, even in the cases where these catalysts are used, there is room for contrivance for preventing the catalyst component tungsten species from being leached into liquid reaction mixtures while maintaining the catalytic activity and efficiency of hydrogen peroxide utilization at high levels.
Further, when efficiency of hydrogen peroxide utilization is low and a catalyst comprising a tungsten species supported on a layered support is used (see e.g. Watanabe, Y. et al. J. Mol. Catal., A: Chemical, (1999), 145 p. 281-289), impurities are formed as byproducts in relatively large amounts and, furthermore, the activity of tungsten species, when supported on such a support, decreases. Thus, there is room for contrivance for making improvements in these respects and thereby improving and maintaining the catalytic activity performance.